Please check these options to fix this problem :
Format > AutoCorrect > While Typing: ON
Tools > AutoCorrect > Options > Options > Capitalize the first letter of every sentence: ON (both M and T)
Document Language (look at the status bar below the editing area); you should see your correct language there, and NOT "None" or nothing.
(I don't think this actually matters for auto-capitalization but it's worth a look anyway.)
File > New > Text Document
Start typing, all lower case. The first space you type, the first word should automatically capitalize.
i hope this will help you